Looked mischievous cutting root (8)
I believe the answer is:
searched
'looked' is the definition.
('search' can be a synonym of 'look')
'mischievous cutting root' is the wordplay.
'mischievous' becomes 'arch' (arch can mean mischievous or playful).
'cutting' is an insertion indicator (some letters cut their way into a word).
'root' becomes 'seed' (I can't justify this - if you can you should believe this answer much more).
'arch' inserted into 'seed' is 'SEARCHED'.
Can you help me to learn more?
(Other definitions for searched that I've seen before include "Sought, looked through" , "Sought, scoured" , "Sought to find" , "Tried to locate" , "Spent time trying to find" .)